18F-THK5351 PET Can Identify Astrogliosis in Multiple Sclerosis Plaques. Ishibashi K, Miura Y, Hirata K, Toyohara J, Ishii K. Clin Nucl Med. 2019 Jul 24. doi: 10.1097/RLU.0000000000002751.
A 26-year-old woman with relapsing-remitting multiple sclerosis (MS) underwent F-THK5351 PET during a remission period. PET imaging showed that small regions with elevated uptake of F-THK5351 were scattered in the brain and that the foci of F-THK5351 accumulations corresponded anatomically to MS plaques identified by MRI. Because F-THK5351 binds to monoamine oxidase B highly expressed in astrocytes, F-THK5351 accumulates in lesions undergoing astrogliosis. Hence, elevated uptake of F-THK5351 in the present case can represent ongoing astrogliosis in inactive MS lesions (plaques).
I read this post with a bit of excitement as it says that it is possible to image astrocytes, using a positron emission topography agent. This is a low grade radioactive drug that can bind to astrocytes. The PET scanner can detect this. They say this drug binds to the monoamine oxidase B receptor. Then I start to be more concerned. A quick look on “Brain Seq” ((CNS tissue RNA expression website) revealed that whilst this could be astrocyte selective, it is not astrocyte specific and could label other cells such as neurons. A quick look at “protein atlas” (protein expression website) for MAOB expression in the brain and it is clearly expressed by more than astrocytes.
This sounds like it could be like TSPO, hailed as being a microglial imager but clearly binding to more than just hot microglia,
Furthermore, they say this “images astrogliosis”, but in the absense of them killing the individual imaged to do some histology, how can they know this? This is a common problem of using imaging of an unknown pathology to define what the image is. Let’s see how this fairs.